Abstract
The relevance of safety applications within the automotive industry is increasing continuously, e.g. due to vehicle automation and decreasing relevance of mechanical backups. To cope with these trends, the power input of safety-related electrical and/or electronic systems needs to be ensured by the power supply system - leading to increased functional safety requirements. Compliance with ISO 26262 will be more in focus in the future. Currently, the compliance with ISO 26262 may be used to argue the state of the art focusing on product liability - however, it will become mandatory for homologation. Thereby, the power supply system is a crucial point since faults of the power supply system are currently the major contributor for vehicle breakdowns with increasing tendency. So far, there is no standard approach within the automotive industry how to ensure functional safety for power supply systems. To fill this gap, this technical elaboration evaluates functional safety with focus on power supply systems development. Hence, guidelines on how to apply the ISO 26262 are provided based on discussions within the automotive industry and research institutes. The focus is on the concept phase, i.e. item definition, hazard analysis and risk assessment, and the functional safety concept. The functional safety concept is based on a structured hierarchical breakdown to systematically derive safety requirements from the item level down to the power supply system level. The essential safety requirement - beside the safe power feed and safe power distribution - is to assure the freedom from interference between the safety and non-safety relevant components.
Highlights
The automotive industry is currently driven by the megatrends electrification and automated driving (AD) respectively advanced driver assistance systems (ADAS)
The following safe state definitions are possible: 1) Steering assistance needs to ensure that the driver is able to perform the minimal risk maneuver until the vehicle is transitioned to standstill based on the original equipment manufacturers (OEM) specific warning and degradation strategy
Melting fuses focus on thermal wiring protection and are not effective safety measures to ensure functional protection of safety relevant ECUs due to undefined and slow separation as well as missing diagnostics
Summary
The automotive industry is currently driven by the megatrends electrification and automated driving (AD) respectively advanced driver assistance systems (ADAS). Each part is either focusing on different phases and/or activities during the safety lifecycle of safety-related E/E systems or provides valuable application guidelines and explanations This technical elaboration presents an approach how to systematically develop a safe power supply system according to ISO 26262, focusing on Part 3 – Concept phase, specifying requirements for: 1) item definition (Section IV-A); 2) hazard analysis and risk assessment (Section IV-B); 3) functional safety concept (Section IV-C). The objective is “to define and describe the item, its functionality, dependencies on, and interaction with the driver, the environment and other items at the vehicle level” [3] This is a crucial point for all subsequent phases: it needs to be ensured that the item under development shall be defined unambiguously to avoid any misunderstandings, including [3]: 1) functionalities, functional behavior and operating modes; 2) boundaries, interfaces and functional dependencies; 3) environmental conditions; 4) legal requirements, national and international standards; 5) known failure modes and hazards. E1 Very low probability less often than once a year for the great majority of drivers
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